PROJECT SUMMARY Episodic memory, or the ability to remember past events with specific detail, is central to the human experience and is related to learning and adaptive functioning in a variety of domains. In typically developing children, episodic memory improves emerges during infancy and improves during early childhood and beyond. Despite remarkable early episodic memory skills, most early recollections are lost to infantile amnesia, individuals' inability to recall events occurred in the first 2 or 3 years of life. Neuroscientific research has shown that the hippocampus plays a fundamental role in episodic memory, supporting the formation and retrieval of representations that bind the different aspects of an event. Of importance, developmental processes within the hippocampus are hypothesized to be primarily responsible for both the early emergence of episodic memory in children and the loss of early recollections due to infantile amnesia. However, these hypotheses are based on non-human models and no direct in-vivo evidence of early hippocampal contribution to early memory functioning and loss is available to date. This limitation is mostly due to the methodological challenge of acquiring neuroimaging data, particularly task-related functional neuroimaging data, from young children. The proposed research will explore new methods to test hippocampal structure and function in toddlers and begin to examine within-individual changes that underlie improvements and loss of episodic memory performance from 25 to 40 months, a period during which episodic memory improves, but infantile amnesia operates. Relevance to Public Health: Healthy episodic memory provides a foundation for the emergence and development of autobiographical memory, continuity of self from past to future, and is associated with the skills assessed in many measures of intellectual ability and achievement. Finally, the development of episodic memory is impaired following even mild forms of acquired neurological insult, mental health conditions such as anxiety and depression, and neurodevelopmental disorders underscoring that a characterization of its development is key to understanding adaptive functioning in various populations of children.